There are two methods for densifying an optical disc. On method is by shortening a channel bit length, i.e., a mark length, in a line density direction. The other method is by narrowing a track pitch. However, when the track pitch is narrowed, information leakage from adjacent tracks (adjacent track cross talk) is increased. There is proposed a method for decreasing the adjacent track cross talk (hereinafter simply referred to a cross talk, as appropriate).
For example, Patent Document 1 describes that a cross talk is cancelled by providing an adaptive equalizer unit with reproduction signals for a track to be reproduced and tracks at both sides of the track to be reproduced and by controlling a tap coefficient of the adaptive equalizer unit.
Patent Document 1: Japanese Patent Application Laid-open No. 2012-079385